Stock-Based Compensation (Restricted Stock Units and PBRSU) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Restricted Stock Units (RSUs) [Member]
Number of Shares
Outstanding, Beginning of Period	1,537,002
RSUs granted	729,731	693,584
RSUs vested	(525,269)
RSUs forfeited	(30,078)
Outstanding, End of Period	1,712,000
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance	$ 32.92
Granted, Weighted Average Grant Date Fair Value	33.83
Vested, Weighted Average Grant Date Fair Value	31.29
Forfeited, Weighted Average Exercise Price	35.14
Weighted Average Grant Date Fair Value, Ending Balance	$ 33.77
PBRSU [Member]
Number of Shares
Outstanding, Beginning of Period	658,839
RSUs granted	174,213	219,378
RSUs vested	(87,981)
RSUs forfeited	(91,139)
Outstanding, End of Period	654,000
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance	$ 29.15
Granted, Weighted Average Grant Date Fair Value	34.29
Vested, Weighted Average Grant Date Fair Value	26.04
Forfeited, Weighted Average Exercise Price	19.50
Weighted Average Grant Date Fair Value, Ending Balance	$ 33.49